Brake systems for towed vehicles (referred to interchangeably herein as “trailers”) typically are electric, pneumatic, or hydraulic, where the level of force applied to the brake drum or rotor is set by the force applied to the brake pad by the actuator. In those conventional systems, release of the brakes, when the tires cease to rotate, is performed by the vehicle operator who releases a brake pedal or a manual control lever. Releasing the brake pedal or manual control lever reduces the force applied to the brake pad by the actuator, thereby allowing the wheels to rotate. In those systems, all of the trailer's wheels generally respond to this single brake force control signal.
Present tow vehicles (e.g., vehicles that tow a trailer) incorporate antilock brake systems (ABSs) to facilitate maintaining control of the tow vehicle by pulsing the braking force applied to the vehicle's wheels when the brake pressure applied by the operator causes the wheels to lock up. This generally is accomplished using electronic wheel speed sensors that monitor the speeds of one or more of the vehicle's wheels and, when a wheel stops rotating, the braking control system releases the pressure to a brake cylinder associated with the wheel, allowing the wheel to rotate again. The ABS quickly reapplies brake pressure and repeats the cycle until the driver releases the brake pedal or the vehicle comes to a stop.
However, the conventional trailer ABS systems still allow for an undesireable amount of skidding and undesireably long stopping times because they typically only release brake pressure in response to detecting that rotation of a wheel has ceased. During the period of time between cessation of the wheel's rotation and the release of the brake pressure, the wheel is not rotating, and thus is skidding. This skidding can lead to tire wear such as, for example, “flat-spotting,” increased stopping times, and the like.